Sectional heat exchanger for use in a heat cell

ABSTRACT

A sectional heat exchanger for a condensing heat cell comprises two end segments and one or more than one intermediate segment(s). The one or the more than one intermediate segment(s) and the two end segments are assembled in the heat exchanger. A combustion chamber is provided in the sectional heat exchanger. Each of the one or the more than one intermediate segment(s) comprises at least one water flow channel for water to be heated. Between each two consecutive segments at least one flue gas flow channel is provided, extending from the combustion chamber. The one or the more than one intermediate segment(s) each comprise a horizontal row of ribs extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heated. Ribs at the two outer sides of the horizontal row of ribs have a larger height than ribs in the middle of the row of ribs. With height of the rib is meant the dimension of the rib in the vertical direction of the sectional heat exchanger. The more than one intermediate segment(s) each comprise a plurality of rows of pins extending in the flue gas channel to increase heat transfer.

TECHNICAL FIELD

The invention relates to the field of sectional heat exchangers for usein a heat cell. Such heat exchangers comprise several segments. Whenassembling the sectional heat exchanger, the number of segments isselected as a function of the required capacity of the sectional heatexchanger. More specifically, the sectional heat exchanger of theinvention has a combustion chamber in which a burner can beinstalled—thereby forming a heat cell—for the generation of flue gasthat will transfer its thermal energy to heat water. Such heat cells canbe used in boilers.

BACKGROUND ART

Sectional heat exchangers are built up of a number of sections orsegments. Sectional heat exchangers, e.g. out of aluminium, exist thatcomprise a number of identical intermediate segments positioned next toeach other; and two end segments. The number of intermediate segmentsthat is used in the assembly of the heat exchanger depends on therequired capacity of the heat exchanger. The heat exchanger has a numberof channels—at least one channel in each intermediate segment—inparallel flow connection for water to be heated, and flue gas channelsextending from the one or more than one combustion chambers in the heatexchanger.

A sectional heat exchanger, using cast intermediate segments, isprovided in DE102005014616B3, in which one single burner can be mountedin the one combustion chamber of the sectional heat exchanger.

GB2441183A discloses a heat exchanger for use in a condensing boilercomprising a plurality of heat exchanger sections having at least oneinternal flow passage with an inlet and an outlet for the passage of aheat exchange medium and a plurality of elongate fins on at least oneside of each section defining flue gas flow channels, a burner toproduce hot flue gas, a means to guide the flue gas from the burnerthrough the flow channels from a primary part to a secondary part of theheat exchanger, and a means to promote unidirectional flue gas flowbefore entering the primary part. Promotion means may be a U-shapedbarrier that changes the flue gas from a radial to the unidirectionalflow and also changes from a downward to an upward flow. The promotionmeans may comprise a plurality of elongated fins disposed between, andparallel to, vertical arms of the U-shape.

DISCLOSURE OF INVENTION

The primary object of the invention is to provide sectional heatexchangers that are less prone to boiling when used in heat cells forboilers.

The first aspect of the invention is a sectional heat exchanger for acondensing heat cell. The sectional heat exchanger comprises two endsegments and one or more than one intermediate segment(s) providedbetween the two end segments. The one or the more than one intermediatesegment(s) and the two end segments are assembled in the heat exchanger.A combustion chamber is provided in the sectional heat exchanger,preferably perpendicular to the one or to the more than one intermediatesegment(s). Each of the one or the more than one intermediate segment(s)comprises at least one water flow channel for water to be heated. Inbetween each two consecutive segments between two intermediate segmentsif more than one intermediate segment is provided as well as betweenintermediate segments and end segments—at least one flue gas flowchannel is provided, extending from the combustion chamber. As aconsequence, flue gas can flow from the combustion chamber into the fluegas flow channels of the sectional heat exchanger. The one or the morethan one intermediate segment(s) each comprise a horizontal row of ribsextending into the flue gas flow channel in order to increase heatexchange from the flue gas to the water to be heated. Ribs at the twoouter sides of the horizontal row of ribs have a larger height than ribsin the middle of the row of ribs. With height of the rib is meant thedimension of the rib in the vertical direction of the sectional heatexchanger. The more than one intermediate segment(s) each comprise aplurality of rows of pins extending in the flue gas channel to increaseheat transfer. Preferably, each row of pins is provided in serial fluegas flow direction. Preferably the pins have a circular cross section.

Preferably, the rib has a substantially rectangular cross section, withits largest side aligned in the vertical direction of the heatexchanger. More preferably, the substantially rectangular cross sectionis a rectangular cross section having rounded edges.

The sectional heat exchanger of the invention has the surprising benefitthat boiling of water in the water flow channels is prevented. Thisbenefit is believed to be achieved thanks to the modified heat exchangeat the horizontal row of ribs because of the differences of height ofthe ribs. The lower height of the ribs in the middle of the row of ribswill obviously involve a reduced heat transfer, negative for efficiencyof the heat exchanger.

Preferably, the intermediate segment is provided such that parallelflows of flue gas flow along all of the ribs of the horizontal row ofribs. Meant is that no gas flow flows first along one rib of thehorizontal row of ribs and then in serial flow arrangement along anotherrib of the horizontal row of ribs.

Preferably, the height over width ratio of each of the ribs of thehorizontal row of ribs is more than 2.

In a preferred embodiment, the one or the more than one intermediatesegment(s) each comprise only one row of ribs extending into the fluegas flow channel in order to increase heat exchange from the flue gas tothe water to be heater.

Preferably, the sectional heat exchanger is a condensing heat exchanger.

In a preferred heat exchanger, ribs in the middle of the row of ribshave less than 70% —more preferably less than 55%—of the height of theribs at the two outer sides of the horizontal row of ribs.

Preferably, the two end segments each comprise a horizontal row of ribsextending into the flue gas flow channel in order to increase heatexchange from the flue gas to the water to be heated. Ribs at the twoouter sides of the horizontal row of ribs have a larger height than ribsin the middle of the row of ribs. With height of the rib is meant thedimension of the rib in the vertical direction of the sectional heatexchanger. In a more preferred embodiment, the two end segments eachcomprise only one row of ribs extending into the flue gas flow channelin order to increase heat exchange from the flue gas to the water to beheated.

Preferably the one or the more than one intermediate segment(s) and/orthe two end segments are aluminium or aluminium alloy segments,preferably separate segments.

Preferably the one or the more than one intermediate segment(s) and/orthe two end segments are cast segments, preferably separate castsegments.

In a preferred embodiment, the sectional heat exchanger comprises atleast two intermediate segments; and the at least two intermediatesegments are provided parallel to each other in the sectional heatexchanger.

In a preferred heat exchanger, at least some ribs in the middle of therow of ribs only partially overlap in height direction the height of thefirst section of the water flow channel located below the combustionchamber. With the first section of the water flow channel located belowthe combustion chamber is meant the elongated full width section of thewater flow channel immediately below the combustion channel. Suchembodiment has shown to synergistically contribute to reduced risk ofboiling of water in the water flow channel.

In a preferred embodiment, the distance between ends in the flue gaschannel of ribs of the row of ribs and ends of ribs positioned on theopposing segment is constant for all ribs in the row of ribs.

Further synergistic effects are obtained by a sectional heat exchangerin which the distance between ends in the flue gas channel of ribs ofthe row of ribs and ends of ribs positioned on the opposing segment isless than 4 mm, and preferably less than 3 mm. Preferably the distancebetween ends in the flue gas channel of each of the ribs of the row ofribs and ends of ribs positioned on the opposing segment is less than 4mm, and preferably less than 3 mm. More preferably, the distance betweenends in the flue gas channel of ribs of the row of ribs and ends of ribspositioned on the opposing segment is constant for all ribs in the rowof ribs.

In a preferred heat exchanger, the row of ribs comprises—and preferablyconsists out of—ribs of a first height and ribs of a second height. Thefirst height is larger than the second height. Ribs at the outer sidesof the horizontal row of ribs are ribs of the first height. Ribs in themiddle of the row of ribs are ribs of the second height. Morepreferably, all other ribs than the ribs of the first height are ribs ofthe second height. Even more preferably, less than 60% of the ribs ofthe row of ribs are ribs of the first height. Even more preferable, lessthan 40% of the ribs of the row of ribs are ribs of the first height. Ina preferred embodiment, the ribs of a second height have less than70%—more preferably less than 55%—of the height of the ribs of a firstheight.

Preferably, the intermediate segment(s) comprise a first horizontal rowof pins below the row of ribs, wherein the pins of the first horizontalrow of pins extend into the flue gas flow channel. With first horizontalrow of pins is meant the horizontal row of pins immediately below therow of ribs. This row of pins comprises at its two outer sides pinsextending into the flue gas flow channel so that a distance of less than4 mm and preferably less than 3 mm—is created with pins extending fromthe opposed segment into the flue gas shaft. This row of pins comprisesin its middle pins extending into the flue gas shaft so that a distanceof more than 10 mm—and more preferably of more than 20 mm—is createdwith pins extending from the opposed segment into the flue gas shaft.Such embodiments contribute synergistically to the prevention of boilingof water in the water flow channel. In a more preferred embodiment,below the first horizontal row of pins, further horizontal rows of pinsextending into the flue gas channel are provided. Preferably within suchhorizontal row of pins, the distance between the pin and the pinextending into the glue gas flow channel from the opposed segment isconstant over the width of the horizontal row of pins.

Preferably, the intermediate segment(s) comprise a plurality ofhorizontal row of pins below the row of ribs, wherein the pins of thehorizontal rows of pins extend into the flue gas flow channel. Each ofthese rows of pins comprises at its two outer sides pins extending intothe flue gas flow channel so that a distance of less than 4 mm andpreferably less than 3 mm—is created with pins extending from theopposed segment into the flue gas shaft. These rows of pins comprise intheir middle pins extending into the flue gas shaft so that a distanceof more than 10 mm—and more preferably of more than 20 mm—is createdwith pins extending from the opposed segment into the flue gas shaft.Such embodiments contribute synergistically to the prevention of boilingof water in the water flow channel.

In a more preferred embodiment, additional horizontal rows of pinsextending into the flue gas channel are provided—preferably below theplurality of rows of pins that extend over different length in the fluegas channel. Within such additional horizontal row of pins, the distancebetween the pin and the pin extending into the glue gas flow channelfrom the opposed segment is constant over the width of the horizontalrow of pins.

Preferably, the combustion chamber has perpendicular to its length axisa cylindrical shape with a circular cross section.

Preferably, the water flow channel in the intermediate segment runs overat least 80% —and more preferably over at least 90%—of the circumferenceof the combustion chamber around the combustion chamber.

Preferably, the sectional heat exchanger comprises at least twointermediate segments. The at least two intermediate segments areprovided parallel to each other in the sectional heat exchanger.

Preferably, in the intermediate segment, the water flow channel followsa meandering flow path.

A preferred sectional heat exchanger comprises more than oneintermediate segment. Water flow channels of the more than oneintermediate segment, and preferably also of the two end segments, areconnected in parallel flow connection.

Preferably, the water flow channels in the one or in the more than oneintermediate segment(s) are provided for counter flow of the water withrespect to the flow direction of the flue gas channels.

A second aspect of the invention is a heat cell. The heat cell comprisesa sectional heat exchanger as in the first aspect of the invention; anda, preferably one, more preferably only one, burner, preferably a premixgas burner, and preferably a cylindrical burner, provided in thecombustion chamber for the production of flue gas to flow in parallelflow connection through the flue gas flow channels between the segmentsof the heat exchanger. The burner is preferably mounted so that itextends in the combustion chamber perpendicularly to the one or to themore than one intermediate segment(s).

Preferably, the heat cell has a condensation sump at the bottom of theheat cell.

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

FIG. 1 shows a heat cell according to the second aspect of theinvention, comprising a sectional heat exchanger according to the firstaspect of the invention.

FIG. 2 shows a view on an intermediate segment of a sectional heatexchanger according to the invention.

FIG. 3 shows a cross section along plane III-Ill of an intermediatesegment of the heat exchanger of FIG. 1.

MODE(S) FOR CARRYING OUT THE INVENTION

FIG. 1 shows a heat cell according to the second aspect of theinvention, comprising a condensing sectional heat exchanger according tothe first aspect of the invention. The figure shows a section 100perpendicularly to the segments of the sectional heat exchanger. FIG. 2shows a view on an intermediate segment of a sectional heat exchangeraccording to the invention. FIG. 3 shows a cross section along planeIII-Ill of an intermediate segment of the heat exchanger of FIG. 1.

The exemplary sectional heat exchanger of FIGS. 1, 2 and 3 comprises twoend segments 102, 104 and two intermediate segments 106 provided betweenthe two end segments 102, 104. The two intermediate segments and the twoend segments are cast aluminum parts and are assembled in the heatexchanger. A cylindrical combustion chamber 108, 208, 308 with acircular cross section is provided in the sectional heat exchanger, inthe example perpendicular to the intermediate segments and perpendicularto the end segments. A cylindrical gas premix burner 110 is provided inthe combustion chamber, perpendicular to the intermediate segments andperpendicular to the end segments.

Each of the intermediate segments 106 and each of the end segments 102,104 comprise a water flow channel 112, 312 for water to be heated. Waterflow channels of the intermediate segments, and preferably also of thetwo end segments, are connected in parallel flow connection. The waterflow channels in the intermediate segments and in the end segmentsfollow a meandering flow path through the segment. The water flowchannels in the intermediate segments as well as the water flow channelsin the end segments run over more than 90% of the circumference of thecombustion chamber around the combustion chamber. The water channels areprovided for counter flow compared to the flue gas flow direction in theflue gas flow channels.

In between each two consecutive segments at least one flue gas flowchannel 114 is provided, extending from the combustion chamber 108, 208,308. The intermediate segments 106 as well as both end segments 102,104—each comprise a horizontal row of ribs 116, 216 extending into theflue gas flow channel in order to increase heat exchange from the fluegas to the water to be heated. Ribs 218 at the two outer sides of thehorizontal row of ribs have a larger height than ribs 220 in the middleof the row of ribs. In the example, the intermediate segments 106 andthe two end segments 102, 104 each comprise only one row of ribs 116,216 extending into the flue gas flow channel in order to increase heatexchange from the flue gas to the water to be heated. In the example,the ribs have a substantially rectangular cross section, with theirlargest side aligned in the vertical direction of the heat exchanger. Inthe exemplary heat exchanger shown in FIGS. 1-3, the ribs 220 at themiddle of the row of ribs of the intermediate segments as well as theribs at the middle of the row of ribs of the end segments have 66% ofthe height of the ribs 218 at the two outer sides of the horizontal rowof ribs. In another exemplary heat exchanger, the ribs 220 at the middleof the row of ribs of the intermediate segments as well as the ribs atthe middle of the row of ribs of the end segments have 50% of the heightof the ribs 218 at the two outer sides of the horizontal row of ribs.

In an exemplary heat exchanger, ribs in the middle of the row of ribsonly partially overlap in height direction the first section of thewater flow channel located below the combustion chamber.

In the example shown in FIGS. 1-3, the distance between ends in the fluegas channel of each of the ribs of the row of ribs and ends of ribspositioned on the opposing segment is 2 mm.

The intermediate segments as well as the end segments comprise a firsthorizontal row of pins 132, 232 below the row of ribs. These pins extendinto the flue gas flow channel. This row of pins 132, 232 comprises atits two outer sides pins extending into the flue gas flow channel sothat a distance of less than 4 mm and preferably less than 3 mm—iscreated with pins extending into the flue gas shaft from the opposedsegment. This row of pins comprises in its middle pins extending intothe flue gas shaft so that a distance of 28 mm is created with pinsextending from the opposed segment into the flue gas shaft.

Below the first horizontal row of pins, further horizontal rows of pins140, 240 extending into the flue gas channel are provided. In theexemplary heat exchanger, the distance between the pin and the pinextending into the glue gas flow channel from the opposed segment isconstant over the width of the horizontal row of pins. In a furtherexemplary heat exchanger, each of the segment(s) comprises a pluralityof horizontal row of pins below the row of ribs, wherein the pins of thehorizontal rows of pins extend into the flue gas flow channel. Each ofthese rows of pins comprises at its two outer sides pins extending intothe flue gas flow channel so that a distance of less than 4 mm andpreferably less than 3 mm—is created with pins extending from theopposed segment into the flue gas shaft. These rows of pins comprise intheir middle pins extending into the flue gas shaft so that a distanceof more than 20 mm is created with pins extending from the opposedsegment into the flue gas shaft.

1. A sectional heat exchanger for a condensing heat cell, wherein thesectional heat exchanger comprises two end segments and one or more thanone intermediate segment(s) provided between the two end segments;wherein the one or the more than one intermediate segment(s) and the twoend segments are assembled in the heat exchanger, wherein a combustionchamber is provided in the sectional heat exchanger, wherein each of theone or the more than one intermediate segment(s) comprises at least onewater flow channel for water to be heated, wherein in between each twoconsecutive segments at least one flue gas flow channel is provided, andwherein the flue gas flow channel extends from the combustion chamber,wherein the one or the more than one intermediate segment(s) eachcomprise a horizontal row of ribs extending into the flue gas flowchannel in order to increase heat exchange from the flue gas to thewater to be heated; wherein ribs at the two outer sides of thehorizontal row of ribs have a larger height than ribs in the middle ofthe row of ribs; wherein with height of the rib is meant the dimensionof the rib in the vertical direction of the sectional heat exchanger;wherein the one or the more than one intermediate segment(s) eachcomprise a plurality of rows of pins extending in the flue gas channelto increase heat transfer.
 2. A sectional heat exchanger as in claim 1,comprising a first section of the water flow channel located below thecombustion channel; wherein at least some ribs in the middle of the rowof ribs only partially overlap in height direction the height of thefirst section of the water flow channel located below the combustionchamber.
 3. A sectional heat exchanger as in claim 1, wherein thedistance between ends in the flue gas channel of ribs of the row of ribsand ends of ribs positioned on the opposing segment is less than 4 mm.4. A sectional heat exchanger as in claim 1, wherein the row of ribscomprises ribs of a first height and ribs of a second height, whereinthe first height is larger than the second height; and wherein ribs atthe outer sides of the horizontal row of ribs are ribs of the firstheight; and wherein ribs in the middle of the row of ribs are ribs ofthe second height.
 5. A sectional heat exchanger as in claim 1, whereinthe intermediate segment(s) comprise a first horizontal row of pinsbelow the row of ribs, wherein the pins extend into the flue gas flowchannel, wherein this row of pins comprises at its two outer sides pinsextending into the flue gas flow channel so that a distance of less than4 mm is created with pins extending from the opposed segment into theflue gas shaft; wherein this row of pins comprises in its middle pinsextending into the flue gas shaft so that a distance of more than 10 mmis created with pins extending into the flue gas shaft from the opposedsegment.
 6. A sectional heat exchanger as in claim 5, wherein theintermediate segment(s) comprise a plurality of horizontal rows of pinsbelow the row of ribs, wherein the pins extend into the flue gas flowchannel, wherein each row of pins comprises at its two outer sides pinsextending into the flue gas flow channel so that a distance of less than4 mm is created with pins extending from the opposed segment into theflue gas shaft; wherein each row of pins comprises in its middle pinsextending into the flue gas shaft so that a distance of more than 10 mmis created with pins extending into the flue gas shaft from the opposedsegment.
 7. A sectional heat exchanger as in claim 1, wherein thecombustion chamber has perpendicular to its length axis a cylindricalshape with a circular cross section.
 8. A sectional heat exchanger as inclaim 1, wherein the water flow channel in the intermediate segment runsover at least 80% of the circumference of the combustion chamber aroundthe combustion chamber.
 9. The sectional heat exchanger as in claim 1,wherein the sectional heat exchanger comprises at least two intermediatesegments and wherein the at least two intermediate segments are providedparallel to each other in the sectional heat exchanger.
 10. Thesectional heat exchanger as in claim 1, wherein in the intermediatesegment(s), the water flow channel follows a meandering flow path. 11.The sectional heat exchanger as in claim 1, wherein the sectional heatexchanger comprises more than one intermediate segment and wherein waterflow channels of the more than one intermediate segment are connected inparallel flow connection.
 12. The sectional heat exchanger as in claim1, wherein the water flow channels in the one or in the more than oneintermediate segment(s) are provided for counter flow of the water withrespect to the flow direction of the flue gas channels.
 13. A heat cell,comprising a sectional heat exchanger as in claim 1; and a burner,wherein the burner is provided in the combustion chamber for theproduction of flue gas to flow in parallel through the flue gas channelsbetween the segments of the sectional heat exchanger.
 14. A heat cell asin claim 13, wherein the burner extends perpendicularly to the one or tothe more than one intermediate segment(s).